The cholinergic influence on the mesenteric ganglion affects the liberation of ovarian steroids and nitric oxide in oestrus day rats: characterization of an ex vivo system

Abstract

The axons that constitute the ovarian nervous plexus originate mostly in the principal neurons of the superior mesenteric ganglion (SMG) that is part of the sympathetic ganglionic chain and exhibits cholinergic receptors. In order to observe the effect of acetylcholine, the main neurotransmitter in the ganglionic transmission, the purpose of the present work was: first, to standardize an integrated ex vivo superior mesenteric ganglion-ovarian nervous plexus-ovary (SMG-ONP-O) system in oestrus day rats; secondly, to determine if the ganglionic cholinergic stimulus modifies the release of nitric oxide and steroids in the ovary compartment in the absence of humoral factors; and thirdly, to investigate if there are differences in the responses between the left and right ovaries caused by the neural stimulus. The ex vivo experimental left and right systems were developed and standardized. The systems were incubated in Krebs-Ringer phosphate buffer in a Dubnoff metabolic shaker. The progesterone release was determined to standardize the incubation times, obtaining different responses between the left and right systems, which shows that both systems have their own autonomic tone. Non-specific stimulation with KCl in the ganglion compartment provoked different responses in terms of release of progesterone and oestradiol. Progesterone decreased in the left and right systems.However, oestradiol diminished at short times and increased at 60 and 120 min in the left ovary, whereas it increases at 30 and 60 min in the right ovary. These different responses show the sensitivity and viability of both systems. When acetylcholine was used in the ganglion compartment, the release of nitric oxide, progesterone, androstenedione and oestradiol was evaluated. The liberation of nitrite increased at 15, 30 and 60 min in the left system and decreased in the right system at 120 min. Progesterone showed a decrease in its release at 15, 30 and 120 min and androstenedione at 15 min in the left ovary compartment. In the right ovary, only progesterone decreased in relation to the control at 120 min while androstenedione did not show significant changes. Oestradiol showed an increase in the left ovary compartment at all the studied times, while in the right ovary it did not show any changes. These results indicate that the neural stimulus from the superior mesenteric ganglion through the ovarian nervous plexus is one of the factors modulating the secretory activity of the ovarian steroids and nitric oxide. The system is viable and also shows a different sensitivity of the left ovary in relation to the right one at least in this cycle stage, characterized by marked irrigation and profound structural changes in the ovary.

Effects of Electrical Stimulation of the Superior Ovarian Nerve and the Ovarian Plexus Nerve on the Ovarian Estradiol Secretion Rate in Rats

“…Therefore we can assume that sympathetic adrenergic vasoconstrictor fibers may travel through both the SON and the OPN to the ovary. Using the ex vivo celiac ganglion-SON-ovary system and the superior mesenteric ganglion-OPN-ovary system, it was demonstrated that a chemical stimulation of the celiac ganglion or superior mesenteric ganglion increases the release of nitric oxide in the ovarian compartment [23,24]. Since an electrical stimulation of the SON and the OPN produces a decrease in ovarian blood flow in the present results, the adrenergic vasoconstrictor effect seems more dominant than the vasodilatory effect of nitric oxide, even if nitric oxide was released in the present experimental condition.…”

Involvement of the oestrogenic receptors in superior mesenteric ganglion on the ovarian steroidogenesis in rat

“…The procedure was carried out between 1500 and 1600 h taking into account previous descriptions of the anatomical trajectory of this neural pathway as a guide (Lawrence & Burden 1980, Klein & Burden 1988a, 1988b, Vega Orozco et al 2006.…”

“…The piece of tissue utilised in this work corresponds to the whole SMG where the principal neurons are located, whose axons constitute the ONP that reaches the ovary, without the presence of the coeliac ganglion (Vega Orozco et al 2006).…”

“…Each cuvette contained 2 ml of work solution, Krebs-Ringer bicarbonate buffer, pH 7.4, in the presence of dextrose (0.1 mg/ml) and BSA (0.1 mg/ml) as described in previous studies (Sosa et al 2000, Vega Orozco et al 2006.…”

“…There is evidence that NO decreases the steroidogenesis in different experimental schemes (Olson et al 1996, Snyder et al 1996, causing an inhibition of the enzymatic activities and gene expression of steroid synthesis-limiting enzymes such as 3b-hydroxysteroid dehydrogenase (3b-HSD) in bovine luteal cells (Rekawiecki et al 2005). Vega Orozco et al (2006) have demonstrated in an ex vivo system that the ganglionic cholinergic stimulus modifies the ovarian steroids and NO release in the oestrus stage.…”